The SY-2 is an improved version of the SY-1. Unlike the SY-1, the
SY-2 does not have a wood grain case. With its black tolex
covering and removable hinged cover, this model was obviously
intended for the gigging musician.

The SY-2 has the same features as the SY-1 except for the
following differences:

The Growlet patch is now called simply "Growl", and the Pulsar patch is now called "Drake". We are unsure if the actual patch changed.

The confusing envelope controls previously referred to as "Attack Bend Tone" are now just "Bend Tone", they still control the filter but nolonger control the VCO on any of the patches. The SY-1 only had "Intensity" and "Time" sliders to control the attack level and rate. Now there is also a slider labeled "decay", which makes the envelope generator much more usable.

There is a new switch labeled pitch-bend, which gives a preset upward slide to pitch at the beginnings of a note.

There is a Foot Control Sensitivity knob now on the front panel, replacing the two knobs on the back panel of the SY-1, and there is a switch to select between the filter cutoff and the volume.

There are new sliders for the high-pass filter for cutoff and resonance. But, like the SY-1, neither filters self-resonate.

As with the SY-1 and its organ cousin the CSY-1, Yamaha also sold a CSY-2 with, presumably, a SY-2 built in.

[Information from The A-Z of Analogue Synthesizers, by Peter Forrest, published by Susurreal Publishing, Devon, England, copyright 1994 Peter Forrest]